Memory card and memory card manufacturing method

ABSTRACT

A memory card includes a first circuit board, a first semiconductor chip mounted to a top face of the first circuit board with a part of its under face confronting the first circuit board, a second circuit board of which a top face is bonded to a under face of the first circuit board, a second semiconductor chip mounted to the top face of the second circuit board with at least a part of the second semiconductor chip confronting a part of another part other than the part of the under face of the first semiconductor chip, and a cover disposed over the top face of the second circuit board for covering the first semiconductor chip, the first circuit board and the second semiconductor chip.

TECHNICAL FIELD

The present invention relates to a memory card and a memory cardmanufacturing method.

BACKGROUND ART

A memory card with a memory chip built therein has been known as one ofrecording media for storing information. Since the memory card isexcellent in portability, it has been widely used as a recording mediumof portable electronic devices such as a portable information terminalor a cell phone.

These portable electronic devices have been downsized and increasedtheir memory capacity year by year in order to improve the portability.This market trend requires the memory card to be downsized and have agreater capacity. In general, the memory card is specified its shape,size, and thickness by the industry standard, so that the memory cardmust meet this standard before it achieves the greater capacity.

To meet the foregoing requirements, a plurality of boards on whichmemory chips are mounted is layered on one face of a base board, and acontrol chip for controlling the operation of the memory chips ismounted on the other face thereof. This structure allows increasing acapacity of the memory card. This technique is disclosed in, e.g. patentdocument 1.

Here is another technique: On a memory chip mounted on a lead frame,another memory chip is layered but shifted therefrom. The electrodes ofthese two memory chips and an electrode of a control chip mounted on thelead frame are coupled to the lead frame via a gold wire, so that thethickness of the memory card can be reduced. This technique is disclosedin, e.g. patent document 2.

However, the memory card disclosed in patent document 1 is limited todecrease its thickness because of the following reason: The memory chipsand the control chip are mounted on different faces of the base board,and the memory boards on which the memory chips are mounted are layeredtogether.

The memory card disclosed in patent document 2 has some restrictions:The memory chips and the control chip are mounted onto the board by awire bonding method, so that the chips, wires, and lead frame need to besealed with thermosetting resin after they are mounted. At this time, asealing layer is to be thick enough for covering the memory chips andthe wires, so that the memory card is limited to be downsized or to bethinner. Since a sealing step is needed in addition to the mountingstep, a reduction in the manufacturing cost is limited. On top of that,the quality of mounting of respective chips cannot be inspected beforeall the chips are mounted to the lead frame, so that if parts of chipsare defective, they cannot be detected before all the chips are mounted.The manufacturing cost is thus obliged to increase.

-   Patent document 1: Unexamined Japanese Patent Publication No.    2003-108963-   Patent document 2: Unexamined Japanese Patent Publication No.    2004-13738

DISCLOSURE OF INVENTION

A memory card of the present invention comprises the following elements:

-   -   a first circuit board;    -   a first semiconductor chip mounted to a top face of the first        circuit board such that only a part of an under face of the        first semiconductor chip confronts the first circuit board;    -   a second circuit board of which top face is bonded to an under        face of the first circuit board;    -   a second semiconductor chip mounted on a top face of the second        circuit board such that at least a part of the second        semiconductor chip confronts a part of another part other than        the part of the under face of the first semiconductor chip; and    -   a cover disposed over the top face of the second circuit board        for covering the first semiconductor chip, the first circuit        board, and the second semiconductor chip.

The foregoing structure allows overlaying the first semiconductor chipover the second semiconductor chip without inserting a circuit boardtherebetween, so that the memory card can be downsized and a thicknessof the memory card can be reduced.

A method of manufacturing the memory card of the present inventioncomprises:

-   -   (a) mounting the first semiconductor chip on the top face of the        first circuit board with only a part of the under face of the        first semiconductor chip confronting the first circuit board;    -   (b) mounting the second semiconductor chip on the top face of        the second circuit board;    -   (c) bonding the second semiconductor chip on the top face of the        second circuit board with at least a part of the second        semiconductor chip confronting a part of another part other than        the part of the under face of the first semiconductor chip; and    -   (d) covering the first semiconductor chip, the first circuit        board, and the second circuit board with the cover disposed over        the top face of the second circuit board.

This method allows manufacturing the memory card in a simply way at abetter productivity and downsizing the memory card as well as reducing athickness of the memory card.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view illustrating a structure of a memory card inaccordance with a first exemplary embodiment of the present invention.

FIG. 2 shows a sectional view cut along line 2-2 in FIG. 1.

FIG. 3A shows a flowchart illustrating a method of manufacturing thememory card in accordance with the first exemplary embodiment of thepresent invention.

FIG. 3B shows a flowchart illustrating a manufacturing method of thememory card in accordance with the first exemplary embodiment of thepresent invention.

FIG. 4A shows a some step of the manufacturing method of the memory cardin accordance with the first exemplary embodiment of the presentinvention.

FIG. 4B shows another some step of in the manufacturing method of thememory card in accordance with the first exemplary embodiment of thepresent invention.

FIG. 4C shows yet another some step of the manufacturing method of thememory card in accordance with the first exemplary embodiment of thepresent invention.

FIG. 5 shows a plan view illustrating a structure of a memory card inaccordance with a second exemplary embodiment of the present invention.

FIG. 6 shows a sectional view cut along line 6-6 in FIG. 5.

FIG. 7 shows a plan view illustrating another structure of a memory cardin accordance with the second exemplary embodiment of the presentinvention.

DESCRIPTION OF REFERENCE MARKS

1, 1 a, 1 b. memory card

2, 2 a, 2 b. first circuit board

3. first semiconductor chip

4. second circuit board

5. second semiconductor chip

6. chip component

7, 7 a. cover

8. fixing member

20. opening

21, 41, 51, 52. top face

22, 32, 42. under face

33, 53. bump

34, 54. sealing resin

71. recess

211, 221, 411, 412, 413. electrode

421. external electrode

S11-S22. step

DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are demonstratedhereinafter with reference to the accompanying drawings. Similarelements in the exemplary embodiments have the same reference marks andthe descriptions thereof are sometimes omitted.

First Exemplary Embodiment

FIG. 1 shows a plan view illustrating a structure of a memory card inaccordance with the first exemplary embodiment of the present invention.FIG. 2 shows a sectional view of the memory card cut along line 2-2 inFIG. 1. In FIG. 1, cover 7 is shown only its outline with dotted linesfor clearly showing the interior structure of memory card 1, and sealingresin to be used for mounting a semiconductor chip is not shown.

In this exemplary embodiment, an SD (Secure Digital) memory card istaken as an example of memory card 1. Memory card 1 has the followingtypical dimensions:

Length: between 14.9 mm and 15.1 mm, (horizontal direction in FIG. 1)

Width: between 10.9 mm and 11.1 mm (vertical direction in FIG. 1)

Thickness: between 0.9 mm and 1.1 mm. (vertical direction in FIG. 2)

Memory card 1 used in this exemplary embodiment has dimensions of 15 mm(L), 11 mm (W) and 1 mm (T). For a convenient purpose of description, anupper side and a lower side in FIG. 2 are referred to as an upper sideand a lower side of memory card 1. The second exemplary embodiment alsouses this naming system.

As shown in FIG. 1 and FIG. 2, memory card 1 comprises the followingelements:

-   -   first circuit board 2 shaped like a picture frame, namely, its        outer circumference and inner circumference form rectangles        respectively;    -   first semiconductor chip 3 mounted to top face 21 shown in FIG.        2, i.e.

the principal face, of first circuit board 2 with ball bump 33sandwiched between top face 21 and first semiconductor chip 3 (the ballbump is called a stud bump, and hereinafter simply referred to as“bump”);

-   -   second circuit board 4 of which top face 41 is bonded to under        face 22 of first circuit board 2;    -   second semiconductor chip 5 mounted on top face 41 of second        circuit board 4 with bump 53 sandwiched between top face 41 and        second semiconductor chip 5;    -   chip component 6, including small components such as resistors,        soldered to top face 41 of second circuit board 4; and    -   cover 7 disposed over top face 41 of second circuit board 4 for        covering first semiconductor chip 3, first circuit board 2,        second semiconductor chip 5, and chip component 6.

The thickness of memory card 1 at a section, where first semiconductorchip 3 and second semiconductor chip 5 are mounted, ranges from notsmaller than 0.6 mm to not greater than 0.8 mm (in this exemplaryembodiment the thickness is 0.7 mm).

Second circuit board 4 is made from glass epoxy (FR-4.5 equivalent) andhas a thickness ranging from not smaller than 01. mm to not greater than0.4 mm (in this exemplary embodiment, the thickness is 0.16 mm). Asshown in FIG. 2, second circuit board 4 includes electrodes 411, 412,and 413 on its top face 41. Electrodes 411 bond to first circuit board2, electrodes 412 bond to second semiconductor chip 5, and electrodes413 bond to chip component 6. Second circuit board 4 further includes aplurality of external electrodes 421 on its under face 42 for connectingto external electronic devices. External electrodes 421 are electricallycoupled to wirings formed on top face 41 of second circuit board 4 viathrough holes (not shown) coupling between under face 42 and top face41.

The thickness of first circuit board 2 ranges from not smaller than 0.1mm to not greater than 0.4 mm (in this exemplary embodiment, thethickness is 0.12 mm). First circuit board 2 includes a plurality ofelectrodes 211 on its top face 21 and along the inner circumference forbonding to first semiconductor chip 3. First circuit board 2 alsoincludes electrode 221 on its under face 22, and electrode 221 issoldered to electrode 411 formed on top face 41 of second circuit board4.

First semiconductor chip 3 and second semiconductor chip 5 are barechips and have thickness ranging from not smaller than 0.05 mm to notgreater than 0.3 mm. First semiconductor chip 3 is a memory chip forstoring information, and second semiconductor chip 5 is a control chipfor controlling first semiconductor chip 3. First semiconductor chip 3includes bump 33 formed on an electrode of under face 32, and sealingresin 34 bonds bump 33 to electrode 211 of first circuit board 2(including a state where a contact therebetween is kept). Secondsemiconductor chip 5 includes bump 53 formed on an electrode of underface 52, and sealing resin 54 bonds bump 53 to electrode 412 of secondcircuit board 4 (including a state where a contact therebetween iskept).

In this exemplary embodiment, sealing resin 34, 54 employ non-conductivefilm (NCF) made of resin such as film-like resin material stuck onto topface 21 of first circuit board 2 or top face 41 of second circuit board4. Sealing resin 34 existing between first semiconductor chip 3 andfirst circuit board 2 surrounds bump 33. Sealing resin 54 between secondsemiconductor chip 5 and second circuit board 4 surrounds bump 53.

Under face 32 of first semiconductor chip 3 shapes like a rectangle, andonly a section shaped like a picture frame and formed along the outercircumference of under face 32 confronts first circuit board 2 (thissection is a vicinity area of the two pairs of edges, each edge of onepair facing to each other, of under face 32). In other words, only apart of under face 32 of first semiconductor chip 3 confronts top face21 of first circuit board 2 in memory card 1.

Second semiconductor chip 5 is placed inside of first circuit board 2with a clearance from the inner circumference of first circuit board 2(refer to rectangular opening 20 of first circuit board 2 shown in FIG.1). Top face 51 of second semiconductor chip 5 confronts under face 32of first semiconductor chip 3 at the vicinity of the center of underface 32 (more specifically a part of another part other than theforegoing part confronting first circuit board 2).

Memory card 1 further includes fixing member 8 disposed between underface 32 of first semiconductor chip 3 and top face 51 of secondsemiconductor chip 5 as shown in FIG. 2. Fixing member 8 works asadhesive for fixing first semiconductor chip 3 and second semiconductorchip 5 to each other.

Cover 7 is formed of molded components made of resin and includes recess71 which accommodates first semiconductor chip 3, first circuit board 2,second semiconductor chip 5, and chip component 6. Cover 7 is mounted tosecond circuit board 4 by using an opening of recess 71.

A method of manufacturing memory card 1 in accordance with this firstexemplary embodiment of the present invention is demonstratedhereinafter. FIGS. 3A and 3B show flowcharts of the manufacturing methodof memory card 1. FIG. 4A-FIG. 4C show a some step of the manufacturingmethod with sectional views of memory card 1 similar to the one shown inFIG. 2 cut along line 2-2 in FIG. 1.

First, as shown in FIG. 4A, form bump 33 on an electrode formed on underface 32 of first semiconductor chip 3 (step S11). Then stick sealingresin 34 such as NCF onto electrode 211 formed on top face 21 of firstcircuit board 2, so that sealing resin 34 is applied to electrode 211(step S12).

Next, hold first semiconductor chip 3 with a mounting device (not shown)such that under face 32 of first semiconductor chip 3 confronts top face21 of first circuit board 2. Then adjust a position of firstsemiconductor chip 3 such that bump 33 confronts electrode 211 viasealing resin 34, and then urge first semiconductor chip 3 against firstcircuit board 2. At this time, only a part (a section shaped like apicture frame along the outer circumference of under face 32) of underface 32 of first semiconductor chip 3 confronts top face 21 of firstcircuit board 2. Then heat first semiconductor chip 3 with firstsemiconductor chip 3 urged against first circuit board 2, and firstsemiconductor chip 3 is electrically coupled to first circuit board 2via bump 33. The heat hardens sealing resin 34, thereby bonding firstsemiconductor chip 3 to first circuit board 2, namely, firstsemiconductor chip 3 is mounted to first circuit board 2 (step S13).Hereinafter, first circuit board 2 with first semiconductor chip 3mounted thereon is referred to as a memory module.

Step S11-step S13 discussed above allow mounting first semiconductorchip 3 onto top face 21 of first circuit board 2 with only a part ofunder face 32 of first semiconductor chip 3 confronting first circuitboard 2.

Next, as shown in FIG. 4B, form bump 53 on an electrode formed on underface 52 of second semiconductor chip 5 (step S14). Then stick sealingresin 54 such as NCF onto electrode 412 formed on top face 41 of secondcircuit board 4, so that sealing resin 54 is applied to electrode 412(step S15).

Next, hold second semiconductor chip 5 with its under face 52confronting top face 41 of second circuit board 4 by using a holder ofthe mounting device. Then adjust a position of second semiconductor chip5 such that bump 53 confronts electrode 412 via sealing resin 54. Thenheat second semiconductor chip 5 while second semiconductor chip 5 isurged against second circuit board 4, and second semiconductor chip 5 iselectrically coupled to second circuit board 4 with bump 53therebetween. The heat hardens sealing resin 54, thereby bonding secondsemiconductor chip 5 to second circuit board 4, namely, secondsemiconductor chip 5 is mounted to second circuit board 4 (step S16).Hereinafter, second circuit board 4 with second semiconductor chip 5mounted thereon is referred to as a control module. Step S14-step S16discussed above allow mounting second semiconductor chip 5 onto top face41 of second circuit board 4.

Next, inspect the memory module and the control module with aninspection device (not shown). To be more specific, apply an electriccurrent to the memory module via first circuit board 2, thereby judgingthe quality of mounting of first semiconductor chip 3 to first circuitboard 2, e.g. good or bad of electrical connection between firstsemiconductor chip 3 and first circuit board 2, or performance of firstsemiconductor chip 3 is electrically inspected (step S17). Run anelectric current to the control module via second circuit board 4,thereby electrically inspecting the quality of mounting of secondsemiconductor chip 5 to second circuit board 4 (step S18).

After the inspection results in normal mounting of the memory module andcontrol module, apply cream solder onto top face 41 of second circuitboard 4 via a mask as shown in FIG. 4C, so that the cream solder isapplied onto electrodes 411 and 413 (step S19). Then apply fixing member8 such as adhesive onto top face 51 of second semiconductor chip 5 (stepS20).

Next, adjust a position of first circuit board 2 such that electrode 221on under face 22 of first circuit board 2 confronts electrode 411 ofsecond circuit board 4 via the solder. Then mount first circuit board 2onto second circuit board 4. In a similar way, mount chip component 6onto electrode 413 formed on second circuit board 4 with solder. At thistime, fixing member 8 on top face 51 of second semiconductor chip 5 isurged by under face 32 of first semiconductor chip 3, so that fixingmember 8 spreads from the space between first semiconductor chip 3 andsecond semiconductor chip 5 into the space around second semiconductorchip 5 as shown in FIG. 2, and fixing member 8 hardens in this state.Then the memory module, the control module and chip component 6 undergoa reflow process. These steps discussed above allow bonding electrode221 on under face 22 of first circuit board 2 to electrode 411 on topface 41 of second circuit board 4 while a vicinity area of a typicalcenter section of under face 32 of first semiconductor chip 3 confrontstop face 51 of second semiconductor chip 5. The typical center arearefers to a part of another area than the part of under face 32confronting first circuit board 2. On top of that, the electrode of chipcomponent 6 is bonded to electrode 413 of second circuit board 4 (stepS21).

Next, mount cover 7 to second circuit board 4, where the memory moduleand chip component 6 are bonded, by using the opening of recess 71. Thisstructure allows covering first semiconductor chip 3, first circuitboard 2, second semiconductor chip 5, and chip component 6 with cover 7,so that memory card 1 is completed (step S22).

On top of that, in the case of detecting a defective mounting of firstsemiconductor chip 3 to first circuit board 2 in step S17, anothernormal memory module is prepared for the defective one, and normalmodules are bonded together. In a similar way, if a defective mountingof second semiconductor chip 5 to second circuit board 4 is detected,another normal control module is prepared for the detective one, andnormal modules are bonded together. The defective modules undergo arepair work, e.g. releasing the bonding of semiconductor chips, orremounting the chips.

As discussed above, according to the first exemplary embodiment, only apart of under face 32 of first semiconductor chip 3 is mounted to topface 21 of first circuit board 2 confronting first semiconductor chip 3.Then first circuit board 2 is bonded to top face 41 of second circuitboard 4, whereby under face 32 of first semiconductor chip 3 confrontssecond semiconductor chip 5 mounted on top face 41 of second circuitboard 4 at a part of another part than the foregoing part of under face32. As a result, first semiconductor chip 3 is layered on secondsemiconductor chip 5 without inserting another circuit boardtherebetween, and memory card 1 thus can be downsized and the thicknessthereof can be reduced.

According to also the first exemplary embodiment, first semiconductorchip 3 is mounted to first circuit board 2 to form a module, and secondsemiconductor chip 5 is mounted to second circuit board 4 to formanother module. Then these modules are layered together. This structureallows inspecting electrically the respective modules before they arelayered, so that the quality of the mounting of first semiconductor chip3 and second semiconductor chip 5 can be judged independently. As aresult, a mounting defective can be detected before the memory module islayered onto the control module, and the manufacturing cost can belowered.

According to conventional art, in the case of mounting a semiconductorchip onto a circuit board by the wire bonding method, the semiconductorchip and the wire need to be sealed with thermosetting resin having alow viscosity after the semiconductor chip is mounted. Thus thethermosetting resin is molded on the top face of the circuit board tocover the semiconductor chips and so on, so that the thermosetting resinsometimes works as a cover of a memory card.

In the first exemplary embodiment, on the other hand, firstsemiconductor chip 3 and second semiconductor chip 5 are mounted in aflip-chip manner onto first circuit board 2 and second circuit board 4respectively with bumps 33 and 53 sandwiched therebetween. Thisstructure not always needs to seal first semiconductor chip 3, secondsemiconductor chip 5 and first circuit board 2 with thermosetting resin,or to form a cover by using the thermosetting resin. As a result, adegree of freedom increases for selecting a material or a manufacturingmethod of the cover. Further, the flip-chip mounting method expectshigher reliability than the wire bonding mounting method. On top ofthat, since first semiconductor chip 3 and second semiconductor chip 5are mounted onto the respective circuit boards via sealing resin 34 and54, it is not needed to seal electrical connections between respectivesemiconductor chips and circuit boards, so that the number ofmanufacturing steps of memory card 1 can be reduced. In this exemplaryembodiment, cover 7 formed of molded components covers firstsemiconductor chip 3, second semiconductor chip 5 and first circuitboard 2. This structure allows simplifying the manufacture of memorycard 1 comparing with the structure where a cover is formed by sealingthose elements with the thermosetting resin.

In this first exemplary embodiment, first semiconductor chip 3 is bondedto first circuit board 2 at the section shaped like a picture framealong the outer circumference of its under face 32, so that firstsemiconductor chip 3 can be rigidly mounted to first circuit board 2.First semiconductor chip 3 is further fixed to top face 51 of secondsemiconductor chip 5 at its under face 32 with fixing member 8 made ofadhesive, so that first semiconductor chip 3 can be further rigidlyfixed, although indirectly, to second circuit board 4.

Second Exemplary Embodiment

A memory card in accordance with the second exemplary embodiment of thepresent invention is demonstrated hereinafter with reference to FIG. 5and

FIG. 6. FIG. 5 shows a plan view illustrating a structure of memory card1 a in accordance with the second exemplary embodiment of the presentinvention. FIG. 6 shows a sectional view of memory card 1 a cut alongline 6-6 in FIG. 5. In FIG. 5, cover 7 a is drawn only its outline withbroken lines in order to show the interior structure of memory card 1 amore clearly, and sealing resin to be used for mounting semiconductorchips is omitted.

As shown in FIG. 5 and FIG. 6, memory card 1 a is equipped with firstcircuit board 2 a different in shape from first circuit board 2 used inmemory card 1 shown in FIG. 1 and FIG. 2. Memory card 1 a includes cover7 a made of thermoplastic resin. The other structures remain unchangedfrom the structure shown in FIG. 1 and FIG. 2, so that they use the samereference marks as those in FIG. 1 and FIG. 2. A manufacturing method ofmemory card 1 a is similar to that of memory card 1, so that thedescription thereof is simplified here.

As shown in FIG. 5 and FIG. 6, first circuit board 2 a is shaped like asquare “C”, to be more specific, first circuit board 2 shown in FIG. 1with its right end opened, namely, the right end of the circuit boardshaped like a picture frame is opened. In memory card 1 a, under face 32of first semiconductor chip 3 confronts top face 21 of first circuitboard 2 a at a vicinity area of a pair of edges of under face 32 andanother edge across the edges at right angles, so that a part of secondsemiconductor chip 5 does not overlap with first semiconductor chip 3.In other words, only a part of top face 51 of second semiconductor chip5 confronts a part of another part other than the foregoing vicinityarea of under face 32.

A method of manufacturing memory card 1 a in accordance with the secondexemplary embodiment is demonstrated hereinafter with reference to FIGS.3A and 3B used in the first exemplary embodiment.

First, form bump 33 on an electrode on under face 32 of firstsemiconductor chip 3, and apply sealing resin 34 to electrode 211 on topface 21 of first circuit board 2 a (step S11 and step S12). Thenelectrically connect first semiconductor chip 3 to first circuit board 2a with bump 33 therebetween, and harden sealing resin 34 thereby bondingfirst semiconductor chip 3 onto first circuit board 2 a (step S13).First semiconductor chip 3 is thus mounted to first circuit board 2 athrough the foregoing steps.

Next, form bump 53 on under face 52 of second semiconductor chip 5, andapply sealing resin 54 to electrode 412 on top face 41 of second circuitboard 4 (step S14 and step S15). Then electrically connect secondsemiconductor chip 5 to second circuit board 4 with bump 53therebetween, and harden sealing resin 54 thereby bonding secondsemiconductor chip 5 onto second circuit board 4 (step S16). Secondsemiconductor chip 5 is thus mounted to top face 41 of second circuitboard 4 through the foregoing steps.

Next, inspect electrically the quality of the mounting of firstsemiconductor chip 3 to first circuit board 2 a via first circuit board2 a (step S17). In a similar way, inspect electrically the quality ofthe mounting of second semiconductor chip 5 to second circuit board 4via second circuit board 4 (step S18).

Then apply solder to electrodes 411 and 413 on top face 41 of secondcircuit board 4 (step S19), and apply fixing member 8 formed of adhesiveto top face 51 of second semiconductor chip 5 (step S20). First circuitboard 2 a and chip component 6 are mounted to second circuit board 4before they undergo a reflow process, so that first circuit board 2 aand chip component 6 are bonded to second circuit board 4 (step S21).

Then form cover 7 a made of thermoplastic resin by an insert moldingmethod for covering first semiconductor chip 3, first circuit board 2 a,second semiconductor chip 5, and chip component 6 on second circuitboard 4. Memory card 1 a is thus manufactured through the foregoingsteps.

As discussed above, according to the second exemplary embodiment andsimilar to the first exemplary embodiment, first semiconductor chip 3can be layered on second semiconductor chip 5 without inserting acircuit board therebetween. Memory card 1 a thus can be downsized andits thickness can be reduced. From the standpoint of downsizing andreducing the thickness of memory card 1 a, at least a part of secondsemiconductor chip 5 can confront a part of another part other than thepart confronting first circuit board 2 a of under face 32 of firstsemiconductor chip 3. This structure allows inspecting electrically thequality of mounting of first semiconductor chip 3 and secondsemiconductor chip 5 individually before a memory module and a controlmodule are layered together, so that the productivity can be improvedand the manufacturing cost can be lowered.

According the second exemplary embodiment and similar to the firstexemplary embodiment, first semiconductor chip 3 and secondsemiconductor chip 5 are mounted in a flip-chip manner, so that a degreeof freedom can increase for selecting a material or a manufacturingmethod of the cover 7 a. Further, the flip-chip mounting method expectshigher reliability than the wire bonding mounting method. Firstsemiconductor chip 3 is bonded to first circuit board 2 a at thevicinity area of three edges of under face 32, so that firstsemiconductor chip 3 can be rigidly mounted to first circuit board 2 a.First semiconductor chip 3 is bonded to second circuit board 4 withfixing member 8 made of adhesive, so that first semiconductor chip 3 canbe further rigidly fixed, although indirectly, to second circuit board4.

According to the second exemplary embodiment, cover 7 a made ofthermoplastic resin allows reducing the rigidity thereof, so that thereliability including safety can be improved.

The exemplary embodiments of the present invention are demonstratedhereinbefore; however, the present invention is not limited to theforegoing exemplary embodiments but various changes as described beloware applicable to the invention: In the exemplary embodiments discussedpreviously, first semiconductor chip 3 and second semiconductor chip 5work as a memory chip and a control chip respectively; however, thepresent invention is not limited to this example. For instance, otherbare chips such as ASIC can be used as first semiconductor chip 3 andsecond semiconductor chip 5. Further, two memory chips are prepared, andthey are layered together as first semiconductor chip 3 and secondsemiconductor chip 5, then they can be controlled by a control chipmounted to another area of second circuit board 4. As secondsemiconductor chip 5, another memory chip that stores information andalso controls other memory chips, i.e. this memory chip does double dutyas a control chip, can be mounted to second circuit board 4. At thistime, the chip can use a semiconductor function in parts, and the chipas a whole does not necessarily include the semiconductor function.

In the previous exemplary embodiments, first semiconductor chip 3 isbonded to first circuit board 2 or 2 a at the outer circumference,shaped like a picture-frame, of its under face 32 or the vicinity areaof three edges of under face 32. However, the present invention is notlimited to these examples. For instance, as shown in FIG. 7, firstcircuit board 2 b formed of two boards placed in parallel with eachother is bonded to second circuit board 4 such that a vicinity area of apair of edges confronting each other of under face 32 of firstsemiconductor chip 3 confronts and bonds to first circuit board 2 b.

In the previous exemplary embodiments, bumps 33 and 53 are formed on theelectrode of first semiconductor chip 3 and the electrode of secondsemiconductor chip 5; however, those bumps can be formed on electrode211 of first circuit board 2 and electrode 412 of second circuit board 4respectively. Other types of bumps such as another ball bump, platedbump, or soldered bump can be used as bumps 33 and 53.

In the previous exemplary embodiments, NCF is used as the sealing resin;however, the present invention is not limited to this example, forinstance, the sealing resin can be formed by applying non-conductiveresin paste, anisotropic conductive resin film, or anisotropicconductive resin paste.

In the previous exemplary embodiments, first semiconductor chip 3 ismounted to first circuit board 2 or 2 a before second semiconductor chip5 is mounted to second circuit board 4; however, the present inventionis not limited to these examples. For instance, second semiconductorchip 5 can be mounted to second circuit board 4 in parallel with themounting of first semiconductor chip 3 to first circuit board 2 or 2 a,or before the mounting of first semiconductor chip 3. The inspection ofthe mounting of first semiconductor chip 3 to the first circuit boardcan be done before the mounting of second semiconductor chip 5 to secondcircuit board 4, or in parallel with the mounting of secondsemiconductor chip 5.

In the previous exemplary embodiments, both of the first and secondsemiconductor chips are mounted in a flip-chip mounting method; however,the present invention is not limited to this example. At least one ofthe two mountings can be done by the wire bonding method when it isneeded. However, from the standpoint of increasing the reliability ofthe mounting or a degree of freedom for selecting a material and amanufacturing method of cover, it is recommended that firstsemiconductor chip 3 and second semiconductor chip 5 be mounted to thecircuit boards by the flip-chip mounting method.

In the previous exemplary embodiments, cover is formed of thermoplasticresin; however, the present invention is not limited to this example.Cover can be formed of thermosetting resin when it is needed; however,from the standpoint of manufacturing memory cards in the simpler way,cover is preferably formed of molded components. On top of that, fromthe standpoint of reducing the rigidity of cover for increasing safety,cover is preferably formed of thermoplastic resin. The memory card ofthe present invention can be used not only as an SD card, but also asother card-shaped memory media such as an IC card.

INDUSTRIAL APPLICABILITY

The present invention is useful for the technical field where memorymedia, such as a memory card for recording information, are required tobe downsized or to be thinner.

1. A memory card comprising: a first circuit board; a firstsemiconductor chip mounted to a top face of the first circuit board suchthat a part of an under face of the first semiconductor chip confrontsthe first circuit board; a second circuit board of which top face isbonded to an under face of the first circuit board; a secondsemiconductor chip mounted on the top face of the second circuit boardsuch that at least a part of the second semiconductor chip confronts apart of another part other than the part of the under face of the firstsemiconductor chip; and a cover disposed over the top face of the secondcircuit board for covering the first semiconductor chip, the firstcircuit board, and the second semiconductor chip.
 2. The memory card ofclaim 1, wherein the first semiconductor chip is mounted to the firstcircuit board with a bump sandwiched between the first semiconductorchip and the first circuit board, and the second semiconductor chip ismounted to the second circuit board with a bump sandwiched between thesecond semiconductor chip and the second circuit board.
 3. The memorycard of claim 1, wherein the cover is formed of a molded component andhas a recess for accommodating the first semiconductor chip, the firstcircuit board, and the second semiconductor chip, and mounted to thesecond circuit board by using an opening of the recess.
 4. The memorycard of claim 1, wherein the cover is made of thermoplastic resin whichis molded such that the first semiconductor chip, the first circuitboard, and the second semiconductor chip are covered with the coverdisposed over the second circuit board.
 5. The memory card of claim 1further comprising a fixing member disposed between the under face ofthe first semiconductor ship and a top face of the second semiconductorchip for fixing the first semiconductor chip and the secondsemiconductor chip to each other.
 6. The memory card of claim 1, whereinthe under face of the first semiconductor chip is rectangular, and avicinity area of at least a pair of edges confronting each other of theunder face confronts the first circuit board
 7. The memory card of claim6, wherein an area shaped like a picture frame along an outercircumference of the under face of the first semiconductor chipconfronts the first circuit board.
 8. The memory card of claim 1,wherein the first semiconductor chip is a memory chip for storinginformation, and the second semiconductor chip is a control chip forcontrolling the first semiconductor chip.
 9. A method of manufacturing amemory card comprising: (a) mounting a first semiconductor chip on a topface of a first circuit board with a part of an under face of the firstsemiconductor chip confronting the first circuit board; (b) mounting asecond semiconductor chip on a top face of a second circuit board; (c)bonding the second semiconductor chip on the top face of the secondcircuit board with at least a part of the second semiconductor chipconfronting a part of another part other than the part of the under faceof the first semiconductor chip; and (d) covering the firstsemiconductor chip, the first circuit board, and the secondsemiconductor chip with a cover disposed over the top face of the secondcircuit board.
 10. The method of manufacturing a memory card of claim 9,wherein step (a) includes: (a-1) forming a bump on one of an electrodeof the first semiconductor chip and an electrode of the first circuitboard; (a-2) applying sealing resin to the electrode of the firstcircuit board; and (a-3) coupling electrically the first semiconductorchip to the first circuit board with the bump between the firstsemiconductor chip and the first circuit board, wherein step (b)includes: (b-1) forming a bump on one of an electrode of the secondsemiconductor chip and an electrode of the second circuit board; (b-2)applying sealing resin to the electrode of the second circuit board; and(b-3) coupling electrically the second semiconductor chip to the secondcircuit board with the bump sandwiched between the second semiconductorchip and the second circuit board.
 11. The method of manufacturing amemory card of claim 9 further comprising: electrically inspectingquality of mounting of the first semiconductor chip to the first circuitboard via the first circuit board, between step (a) and step (c); andelectrically inspecting quality of mounting of the second semiconductorchip to the second circuit board via the second circuit board, betweenstep (b) and step (c).